Field of the Invention
The present invention relates to an imaging apparatus represented by a digital camera and, more particularly, to an imaging apparatus having a refocus function and a continuous photographing function.
Description of the Related Art
In the related arts, among a digital camera and the like, there is an apparatus which can perform a continuous photographing. If a phase difference detection method used in, for example, a single lens reflex camera or the like is performed as an auto focus (hereinbelow, referred to as AF) during the continuous photographing, an arithmetic operation of the AF can be performed at a relatively high speed and an image in which each frame thereof is AF-controlled can be picked up. However, since there is a time lag between an accumulation operation of an AF sensor and an exposure of an imaging element, particularly, with respect to an object which moves at a high speed, even if the AF control is performed on the basis of an output accumulated in the AF sensor, the object moves during the time lag that the image pickup has. Thus, such a phenomenon that the image is defocused at the time of the image pickup can occur. Therefore, in the Official Gazette of Japanese Patent Application Laid-Open No. 2001-21794 (Patent Literature 1), such a technique that a focus position at the time of exposure of the imaging element is predicted from a plurality of past AF results, the focus position is corrected by an amount corresponding to the considered time lag, and a focus lens is moved is proposed.
An imaging apparatus having such a construction that a microlens array is arranged on a front surface of an imaging element at a rate in which one microlens is provided for a plurality of pixels, thereby enabling information of an incidence direction of a ray of light which enters the imaging element (also known as “light field data”) to be also obtained is proposed in Ren Ng, et al., “Light Field Photography with a Hand-Held Plenoptic Camera”, Stanford Tech Report CTSR 2005-02 (Non-Patent Literature 1) or the like. As a use of such an imaging apparatus, besides a use in which an ordinary photographed image is generated on the basis of an output signal from each pixel, such a use that by executing a predetermined image processing to a photographed image, an image focused to an arbitrary focal distance can be reconstructed or the like can be also considered.
However, the related art disclosed in Patent Literature 1 has such a problem that, for example, like a fall accident scene which occurs in the photographing of a motorcycle race scene or the like, in the case of an object which changes suddenly a speed of motion thereof or the like, it is difficult to predict a focus position and it is difficult to execute the accurate AF operation. Further, since the AF control is made to a target object, for example, if an attention is paid to one object which is running in a race scene, it is fundamentally impossible to photograph an image focused to another object which is running after the target object.
Also in the technique disclosed in Non-Patent Literature 1, a focal distance at which an image can be reconstructed is limited by a construction of an imaging apparatus and, generally, an image focused to all object distances in a range from the nearest side to the infinite side cannot be always reconstructed.
It is, therefore, an aspect of the invention to provide an imaging apparatus which can obtain a desirably-focused image even at the time of a continuous photographing of an object which changes suddenly a speed of motion thereof.